ERBB2 and neoplasm: Luminal B tumours are ER-positive, but may have variable degrees of ER/PgR expression; histologically, they are high-grade and have high cell proliferation.3 Approximately 20% of luminal B tumours are HER2-positive and treated with anti-HER2 therapeutics, but patients with luminal B/HER2-negative tumours need to be accurately diagnosed and receive adjuvant chemotherapy.